The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a multilateral completion system utilizing an alternate passage.
In typical multilateral completion systems, a whipstock, milling guide or other type of deflector is set in a casing string in a main or parent wellbore to deflect a mill to form a window through a sidewall of the casing string. After the milling operation, the whipstock or another deflector may then be used to deflect drill bits and other tools through the window to form a branch or lateral wellbore. The whipstock or another deflector may then be used to deflect a liner string into the branch wellbore.
The liner string is cemented in the branch wellbore. An upper portion of the liner string in the main wellbore is then cut off and retrieved from the well. The whipstock or other deflector is then retrieved from the well to permit access to a lower portion of the main wellbore.
It will be appreciated that it would be beneficial to eliminate the time and expense involved in cutting off the upper portion of the liner string, retrieving it from the well, and retrieving the whipstock from the well. It would also be beneficial to provide improved isolation between the casing and liner strings and a formation surrounding the intersection between the main and branch wellbores.